Field of the Invention
The present invention relates to a power seat sliding apparatus that slides a seat with respect to a floor using motors.
Description of the Related Art
There is a power seat sliding apparatus that slides a seat using motors, for example, as is shown in FIGS. 13 and 14.
FIG. 13 is a longitudinal cross section of a power seat sliding apparatus in the related art. FIG. 14 is an enlarged view of a support member portion of FIG. 13. Referring to these drawings, a lower rail 1 installed on a floor side is engaged in a movable manner with an upper rail 3 on which to install a seat.
A threaded rod 5 that is male-threaded on a peripheral surface is installed to the upper rail 3 along a longitudinal direction.
A gearbox 7 is provided at one end of the upper rail 3. Installed in the gearbox 7 is a gear reduction mechanism formed of a worm 9 driven by an unillustrated motor and a worm wheel 11 that meshes with the worm 9. One end of the threaded rod 5 is connected to the worm wheel 11 on an output side of the gear reduction mechanism. The other end of the threaded rod 5 is supported in a rotatable manner on the upper rail 3 with an unillustrated bearing bracket.
A nut member 13 is fixed to the lower rail 1 using a bracket 15. The nut member 13 is provided with a through-hole 13a that is female-threaded on an inner peripheral surface. The threaded rod 5 is threaded into the through-hole 13a of the nut member 13.
Hence, the upper rail 3 moves along the lower rail 1 as the threaded rod 5 is driven to rotate by the unillustrated motor.
In the power seat sliding apparatus configured as above, a load acting on the seat is transmitted to the floor sequentially through the upper rail 3, the threaded rod 5, the nut member 13, the bracket 15, and the lower rail 1. Herein, suppose that a load is transmitted from the upper rail 3 to the threaded rod 5 via the gear box 7, the gearbox 7 may possibly undergo deformation or break. In consideration of this inconvenience, a load transmission mechanism 21 is provided to lessen a load transmitted by way of the gearbox 7.
The load transmission mechanism 21 will now be described using FIG. 13 and FIG. 14.
The worm wheel 11 of the gearbox 7 and the threaded rod 5 are connected by means of serration so that the worm wheel 11 and the threaded rod 5 are allowed to move freely in an axial direction.
A washer 23 and a washer 25 as a first load transmission member are fixed to the threaded rod 5 with a space in between. A support member 27 as a second load transmission member is installed between the washer 23 and the washer 25. The support member 27 is formed of a main body portion 27b provided with a through-hole 27a having an inner diameter set larger than an outer diameter of the threaded rod 5 and an attachment portion 27c formed continuously from the main body portion 27b and attached to the upper rail 3 using a nut 29. The threaded rod 5 is inserted into the through-hole 27a of the support member 27.
Each of the main body portion 27b of the support member 27, the washer 23, and the washer 25 is formed as follows:
(1) a first surface 23a of the washer 23, which is a surface opposing the washer 25, abuts on a third surface 27d of the main body portion 27b of the support member 27, which is a surface opposing the first surface 23a of the washer 23; and
(2) a second surface 25a of the washer 25, which is a surface opposing the washer 23, abuts on a fourth surface 27e of the main body portion 27b of the support member 27, which is a surface opposing the second surface 25a of the washer 25.
When configured in this manner, most of a load transmitted from the upper rail 3 to the floor is transmitted to the floor sequentially through the support member 27, the washer 23 or the washer 25, the threaded rod 5, the nut member 13, the bracket 15, and the lower rail 1. An example of this configuration is described, for example, in JP-A-2007-55557.